chore!: bump bignum to 0.7.4 (#88)

Author: TomAFrench

Nargo.toml

@@ -5,5 +5,5 @@ authors = [""]
 compiler_version = ">=1.0.0"
 
 [dependencies]
-bignum = { tag = "v0.7.3", git = "https://github.com/noir-lang/noir-bignum" }
+bignum = { tag = "v0.7.4", git = "https://github.com/noir-lang/noir-bignum" }
 poseidon = { git = "https://github.com/noir-lang/poseidon", tag = "v0.1.1" }